POS0391 TRENDS IN THE DIAGNOSIS OF MYOSITIS AND ASSOCIATION WITH THE CORONAVIRUS-19 PANDEMIC AND VACCINES: DATA FROM THE VENETO RARE DISEASE REGISTRY, 2014-2021
Authors: A. Giollo, M. Zen, M. Gatto, E. Zanatta, L. Iaccarino, A. Doria
Journal: Annals of the Rheumatic Diseases (2022)

Background There are uncertainties regarding the occurrence of idiopathic inflammatory myopathies (IIM) after infection by Severe Acute Respiratory Syndrome (SARS)-CoronaVirus2(CoV2) or in recipients of Coronavirus disease-19 (Covid-19) vaccines. Objectives Herein, the main objective was to assess temporal trends of newly diagnosed IIM in the past eight years, including the effects of the Covid-19 pandemic. Methods We extracted data of IIM patients from the Veneto Rare Disease Registry from 01/01/2014 and 31/12/2021. This regional registry has to be considered comprehensive of all patients with IIM in a specific geographical area. Hence, we extracted the following information: age; sex; date of diagnosis; type of IIM including dermatomyositis (DM), polymyositis (PM), anti-synthetase syndrome (ASS), inclusion body myositis (IBM); place of residence. We restricted the analysis to IIM patients certified by expert rheumatologists belonging to the Regional Centre for Study and Treatment of Connective Tissue and other Rare Diseases at the Division of Rheumatology, University of Padua, Veneto, Italy. Finally, we compared new IIM cases before and after 04/01/2021 as the starting date for the vaccination campaign in Veneto. We reported descriptive statistics (median and interquartile range) and results of non-parametric tests to compare cases of IIM across the study period. Results Database extraction retrieved 192 people with IIM diagnosed during the study period (DM 85, PM 82, ASS 23, IBM 2; females 67.2%; median [25 th -75 th percentile] age at diagnosis 58.5 [49.6-68.5] years). There was a median of 2 [1-4] newly-diagnosed IIM monthly, with a non-significant increase in the post-pandemic two-year period 2020-2021 (Figure 1 A ). Numerically, 2020 had the most IIM diagnosis (N=30), mainly clustered in the second (N=12) and third (N=11) trimesters. Trends of new IIM diagnoses over one year course were similar during the study period, with visually identified higher IIM occurrence in February, April and September (Figure 1 B ). There was no difference in incident IIM cases in the 12 months before (N=31) and after (N=29) the initiation of the vaccination campaign (7 [5-9.8] vs 8 [3-12] new cases for each trimester; Mann-Whitney U test p=0.884). Finally, there was a significant trend for median age at diagnosis increasing by 6.46 years from 55.4 to 61.8 years between 2014 and 2021 (p=0.015, R 2 =0.344; repeated measures ANOVA with post test for linear trend). Conclusion We found no significant change in patterns of IIM diagnoses between 2014 and 2021 besides a slight numerical increase in the second and third trimesters of 2020. In addition, we noted no signals of increased IIM diagnoses after introducing Covid-19 vaccines. This data encourage further analyses of larger, multicentre datasets from other geographical areas to clarify whether there has been variation in specific myositis subtypes across new-onset IIM after the pandemic. Acknowledgements We acknowledge Dr Monica Mazzuccato and Registro Malattie Rare - Regione Veneto for providing data. Disclosure of Interests None declared